Process of manufacture of incandescent lamp



N. P. DEMAS PROCESS OF MANUFACTURE OF INCANDESCENT LAMP Filed Sept. 1B,1964 ATTORN EYS United States Patent O 3,341,272 PROCESS F MANUFACTURE0F INCANDESCENT LAMP Nickolas P. Demas, Cranford, NJ., assignor toWagner Electric Corporation, a corporation of Delaware Filed Sept. 18,1964, Ser. No. 397,401 6 Claims. (Cl. 316-17) The present inventionrelates to the manufacture of incandescent lamps and comprises a novelprocess which as compared to processes heretofore in use, issubstantially simpler and results in lamps having pure gas fills and ofconsistently higher quality.

The process of the invention omits all stages of lamp manufacture inwhich the lamp bulb is exhausted. This reduction in the number ofoperating stages substantially lowers manufacturing costs and eliminatesdanger of oil vapor contamination resulting from use of vacuum pumps andoil sealed rotary valves. In the new process no exhaust tube is requiredand therefore butt seals are not required and sealing alloys other thandumet can be employed for the leading in wires. The new processtherefore saves not only equipment but also labor and moreover resultsin a superior product. Briefly, the invention comprises the use of aflush tube for driving out air from the envelope which is to form thelamp bulb and for replacing the driven out air with a flush gas. Theflush tube is introduced into an open end of the envelope and thenwithdrawn during the fusing and pinching of the open end to form thefinal seal. The rate of introduction of flush gas into the envelope isso controlled as to avoid turbulence. A uniform fill of gas and tighthermetic seal of the lamp is obtained.

For a better understanding of the invention and of the advantagesthereof reference may be had to the accompanying drawing of which- FIGS.1 through 6 represent sucecssive stages of the process of the inventionas applied to the manufacture of a cartridge type lamp; and

FIGS. 7 and 8 represent the process as applied to a single ended type oflamp.

In the drawing, the various means for supporting the parts have beenomitted as it will be understood that conventional rotary type lampmaking machinery having means at each stationary for supporting the lamppar will be employed.

In FIG. 1 there is illustrated diagrammatically a tubular glasscontainer 2 having reduced neck or end portions 4. This represents thefirst stage wherein the container or envelope 2 is loaded on to themachine.

In FIG. 2 the envelope 2 is shown with a filament 6 disposed axiallytherein and with lead-in wires 8 and 10 connected to the filament 6 andextending through the neck portions 4. At this stage in the process themount comprising the lfilament and lead wires is suitably supported soas to -be disposed within the envelope 2. In the next step ofthe-process the lower neck 4 is heated and pressed together to fuse theglass about the lead 10 and seal the lower end of the envelope. Theprocess so far described is conventional in the ordinary and presentlyused process of lamp manufacture. Following the stage represented byFIG. 3 in conventional practice, an exhaust tube would be butt sealed tothe upper neck 4 and the envelope 2 would be repeatedly exhausted andflushed prior to the nal filling with fill gas and tipping off of theexhaust tube. In accordance with the present invention these varioussteps are omitted and instead, as shown in FIG. 4, a iiush tube 12 ofrelatively small diameter, for example, of .050 with a bore of .030", isinserted through the upper open neck 4 of the envelope 2 to a depthadjacent the lower end of the filament 6. An inert -gas of approxi-3,341,272 Patented Sept. 12, 1967 ICC mately 88% argon is introducedinto the tube 12 from a suitable source of supply at a relatively slowrate, for example, at a rate of one cubic foot per hour. During theintroduction of the inert gas the upper neck is heated to soften theglass and at the end of approximately 30 seconds the flush tube 12 israised and withdrawn from the envelope 2 while the fused upper neck 4 ispinched to seal the envelope and secure the lead 3 therein. The supplyof a flush gas is turned oft just prior to removal of the flush tube 12from the envelope 2. FIG. 5 illustrates this final step of removal ofthe flush tube and pinching of the fused neck 4 and FIG. 6 illustratesthe completed cartridge type lamp.

FIGS. 7 and 8 represent the process of the invention as employed in themanufacture of small gas filled single ended lamps such as indicator orread-out lamps. In these figures the flush tube 12 is shown as extendingthrough the open neck 1-6 of a bulb 20 to a point adjacent the lowerclosed end of the bulb. As shown best in FIG. i8 which is a view takenat right angles to that of FIG. 7, the tube 12 clears the filament 22and glass buttons 24 fused about the lead-in wires 26 of the lamp. Asdescribed in connection with the cartridge type lamp, inert gas isintroduced through the tube 12 into the bulb to displace the air thereinand fill the bulb with the inert gas. The neck 16- of the bulb is heatedand, while withdrawing the tube, the fused neck is pinched to seal thebulb and secure the lead-in wires in the press.

From the foregoing description taken together with the drawing, it willbe apparent that the present process eliminates many -conventional stepsin the manufacture of gas filled lamps and that the elimination of suchsteps provides the following advantages over conventional manufacturingprocesses:

(l) Elimination of vacuum pumps.

(2) Elimination of rotary oil sealed valves as used on presentproduction exhaust machines.

(3) Elimination of oil vapor contamination of internal lamp parts due tooil vapors from vacuum pumps and oil sealed rotary valves.

(4) Elimination of Vacuum type connections such as are used on presentexhaust equipment.

(5) Elimination of exhaust tube.

(6) Elimination of exhaust tube tipping operation.

(7) Eliminationof butt seals and consequently the opportunity for use ofsealing alloys other than dumet wire.

Prior to the present invention it had been assu-med that a pure gas fillin a lamp could only be effected after the lamp had been completelyevacuated of all air and moisture and for this reason processesheretofore in use have included at least two stages of evacuation. Inaccordance with the present invention it has been found that providedthe rate of introduction of the fill gas is not too rapid, the air andmoisture can be completely driven out of the envelope by theintroduction of the fill gas and that this can be effected in arelatively short period of time. In FIGS. 4 and 7 the dashed linesissuing from the lower end of the flush tube 12 represent the directionof flow of, first, the air in the tube and then of the fill gas whichreplaces the air during the process.

It will be apparent from the foregoing description that the new processof manufacturing gas lled lamps is not only cheaper and simpler topractice but results in a superior product.

The following is claimed:

1. A process of manufacturing an incandescent lamp which comprises thesteps of flowing a stream of fill gas into the open neck of a heatfusible envelope containing a filament, said open neck constituting thesole opening in said envelope, delivering said flowing gas stream to anend of said envelope remote from said open neck, reversing the directionof ow of said gas stream at said remote end back towards said open neckand spreading said gas stream laterally at a rate of flow sucient tocompletely displace air from said envelope but insufficient to causeturbulence, fusing said open neck when said envelope has been filledwith said ll gas, and uniting the walls of said fused open neck about atleast one lead-in wire for said filament, said method being carried outwithout refrigerating said fill gas in order to condense it into liquidform.

2. A process as in claim 1 wherein the point of delivery of ll gas isgradually withdrawn from the envelope.

3. A process in claim 1 wherein the fill gas is substantially pureargon.

4. A process as in claim 1 wherein the fill gas is delivered at the rateof approximately one cubic foot per hour.

5. A process as in claim 1 wherein the ll gas is delivered for aboutthirty seconds at the rate of approximately one cubic foot per hour.

6. A process as in claim Z wherein the flow of said gas stream isstopped just prior to withdrawal of the point of delivery thereof fromsaid envelope.

References Cited UNITED STATES PATENTS 3,162,499 1'2/ 1964 Gustin S16-24RICHARD H. EANES, JR., Primary Examiner.

1. A PROCESS OF MANUFACTURING AN INCANDESCENT LAMP WHICH COMPRISES THESTEPS OF FLOWING A STREAM OF FILL GAS INTO THE OPEN NECK OF A HEATFUSIBLE ENVELOPE CONTAINING A FILAMENT, SAID OPEN NECK CONSTITUTING THESOLE OPENING IN SAID ENVELOPE, DELIVERING SAID FLOWING GAS STREAM TO ANEND OF SAID ENVELOPE REMOTE FROM SAID OPEN NECK, REVERSING THE DIRECTIONOF FLOW OF SAID GAS STREAM AT SAID REMOTE END BACK TOWARDS SAID OPENNECK AND SPREADING SAID GAS STREAM LATERALLY AT A RATE OF FLOWSUFFICIENT TO COMPLETELY DISPLACE AIR FROM SAID ENVELOPE BUTINSUFFICIENT TO CAUSE TUBULENCE, FUSING SAID OPEN NECK WHEN SAIDENVELOPE HAS BEEN FILLED WITH SAID FILL GAS, AND UNITING THE WALLS OFSAID FUSED OPEN NECK ABOUT AT LEAST ONE LEAD-IN WIRE FOR SAID FILAMENT,SAID METHOD BEING CARRIED OUT WITHOUT REFRIGERATING SAID FILL GAS INORDER TO CONDENSE ITO INTO LIQUID FORM.